What is an Alternator

“Oh it’s probably your alternator mate, it’s probably knackered.”

Well that’s great news, I don’t even know what an Alternator is, let alone know how to check it or replace it.

Well hopefully we can shed a little light onto this matter with the article below.

What is an alternator ? – Simply put ;An alternator is a generator. It generates an electrical current.

When does it do this ? – It will generate an electrical current when the engine is running.

Here are a couple of photos ;

What does it do with the electrical current ?
It sends it back into the battery, it recharges it.

Why do I need an alternator ?
Because if the battery was not recharged, there would be no power to run the car. If you took a fully charged battery and put it onto your car, the car would start and continue to draw power out of the battery (i.e. for the spark plugs in a petrol engine). Eventually the battery will run flat (no power) and the engine will stop.

Think of it like a full circle ;
Battery starts the engine – Engine turns the alternator – Alternator recharges the battery.

Where is my Alternator ?
On every car I have owned, the alternator has been on the left side at the front of the engine bay when looking from the front of the car.

How do alternators work ?
The alternator is bolted to the side of the engine and is driven (turned) by the engine via a belt.The belt turns a shaft inside the alternator when the engine is running and the output (voltage) is sent to the battery via wires.

Alternators are relatively easy to change and many places sell brand new replacements as well as reconditioned or refurbished items. A reconditioned alternator has had all the internal wear parts such as brushes replaced with new ones. They will have been tested and will come with a guarantee.

I have also fitted second hand (used) alternators to a number of my cars. These have been sourced from scrap yards or vehicle dismantlers. They normally come with a receipt and can be changed within a short period of time if they turn out not to be working. I have always asked the supplier to test the alternator before I have paid for it. When buying parts it is always very important to keep the receipts incase a problem occurs.

Receipts are always worth keeping as they show a history of your car which prospective buyers like to see when they are thinking of buying your vehicle.